Plastic film mulching has played an important role in Chinese agriculture due to its soil warming
and moisture conservation effects. With the help of plastic film mulch technology, grain and cash
crop yields have increased by 20–35% and 20–60%, respectively. The area of plastic film
coverage in China reached approximately 20 million hectares, and the amount of plastic film
used reached 1.25 million tons in 2011. While producing huge benefits, plastic film mulch
technology has also brought on a series of pollution hazards. Large amounts of residual plastic
film have detrimental effects on soil structure, water and nutrient transport and crop growth,
thereby disrupting the agricultural environment and reducing crop production. To control
pollution, the Chinese government urgently needs to elevate plastic film standards. Meanwhile,
research and development of biodegradable mulch film and multi-functional mulch recovery
machinery will help promote effective control and management of residual mulch pollution.
‘White revolution’ to ‘white pollution’—agricultural plastic film mulch in China
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3. Environ. Res. Lett. 9 (2014) 091001 E K Liu et al
Figure 1. Plastic film mulching field in Tongchuang, Shaanxi and plastic mulch residue field in Shihezi, Xijiang, China.
intensity, with increase ranging from three- to ten-fold. The
Northern regions exhibited greater growth, with higher
absolute intensity. For example, the plastic film mulch use
intensity in Xinjiang increased from 7.0 kg hm−2 in 1991 to
34.8 kg hm−2 in 2011(1 kg plastic film can cover 150–250 m2
area). Over the next ten years, the cultivation area covered by
plastic film mulch is expected to increase at a rate of 8–10%,
with the covered crop area increasing from the current 20
million hm2 to above 30 million hm2 and plastic film mulch
usage increasing from the current 1.2 million tons to above
two million tons.
Despite benefits of plastic film mulch technology, how-ever,
its widespread use has generated large amounts of
mulch residue. As a result, the application of plastic film
mulch technology is evolving from ‘white revolution’ to
‘white pollution’ (figure 1). Since plastic film mulch is mainly
composed of polyvinyl chloride, the residual mulch film does
not readily degrade in soil. The problem is worsened by the
low rate of plastic film mulch recovery due to mechanized
cultivation and thin film (less than 0.008 mm). Investigation
of the major plastic film mulch use areas in China indicated
soil residual mulch levels of 50–260 kg hm−2 in arable lands
with long-term plastic film mulch cover (over ten years) [2].
Large amounts of residual mulch film can lead to unsustain-able
farmland use and thereby affect the agricultural envir-onment
[2, 4]. The main considerations are as follows. (1)
Effect on moisture and nutrient transport in soil. These
changes primarily reflect the damage to the physical structure
of soil by residual mulch, which blocks the infiltration of
capillary water and natural water and affects the moisture
absorption in soil. As a result, nutrient movement speed and
moisture penetration are reduced. (2) Effect on crop emer-gence
and root growth. Studies in Xinjiang showed that
residual plastic film mulch levels of 200 kg hm−2 in the top-soil
(0–20 cm) affected the emergence rate of cotton seeds and
reduced cotton production by 15%. (3) Secondary salinization
of soil. Studies showed that mulching for 5–20 consecutive
years led to a 122–146% increase in the salt content of the
topsoil. (4) Degradation of polyethylene residual mulch film
is negligible with the possible formation of environmentally
harmful chemical products such as phthalate esters [5], di-(2-
ethylhexyl) phthalate, aldehydes and ketones.
Scientists in China have recognized the hazards from
plastic film mulch pollution and taken measures to address the
problem of residual plastic film mulch. However, due to
technical and economic limitations, it remains difficult to
apply these measures at a large-scale. Residual plastic film
mulch pollution has become a serious issue and needs to be
addressed from aspects of policy, regulation and technology
in an all-round manner. (1) Improve mulch film standards and
the relevant quality control mechanisms to increase mulch
film recovery and enhance mulch film recycling [5]. The
mulch film currently used in China is less than 0.008 mm
thick; in contrast, the mulch film used in the US and European
countries are generally 0.020 mm and in Japan 0.015 mm. In
these countries, the better quality mulch film remains mostly
intact after use, and nearly no residual plastic film mulch is
left in farmland soil after mechanized recovery. (2) Accelerate
development of biodegradable mulch film with reduced pro-duction
cost to replace the mulch film most commonly used at
2
4. Environ. Res. Lett. 9 (2014) 091001 E K Liu et al
present [6], which is primarily composed of polyvinyl
chloride. (3) Accelerate research and development of light-weight,
simple and multi-functional machinery for residual
mulch film recovery. The key focus should be farm machin-ery
and technical measures that can be used for both regular
farming operations (such as plowing) and residual mulch film
recovery. Thus, highly efficient mulch film recovery should
be achieved without increasing operation cost and burden on
farmers.
Plastic film mulching technology provides good water
retention and warming effects. If residual mulch film pollu-tion
can be effectively controlled in China, the application of
plastic film mulching technology in this country will provide
a useful reference for improving crop yield and water use
efficiency in other similar regions worldwide, particularly in
regions with cold and arid climates.
Acknowledgments
We thank Professor B H So for useful comments. Partial
support came from National Natural Science Foundation of
China (31370522), 12th five-year plan of National Key
Technologies R&D Program (No. 2012BAD09B01) and
‘948’ project from Ministry of Agriculture (2014-Z6).
References
[1] Zhang F S, Chen X P and Vitousek P 2013 Chinese agriculture:
an experiment for the world Nature 497 33–5
[2] Yan C R, He W Q and Mei X R 2010 Agricultural Application
of Plastic Film and its Residue Pollution Prevention
(Beijing, China: Science Press)
[3] National Bureau of Statistics of China China Statistical
Yearbook (Beijing, China: China Statistics Press) from 1982
to 2012
[4] Chang R P and Yan C Y 2012 Research Report on Overall
Current Situation on Agricultural Plastics Residuals
Pollution and its Countermeasures (Beijing, China: China
Agricultural Science and Technology Press)
[5] Chen Y, Wu C, Zhang H, Lin Q, Hong Y and Luo Y 2013
Empirical estimation of pollution load and contamination
levels of phthalate esters in agricultural soils from plastic
film mulching in China Environ. Earth Sci. 70 239–47
[6] Kyrikou I and Briassoulis D 2007 Biodegradation of agricultural
plastic films: a critical review J. Polym. Environ. 15 125–50
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